The present invention relates generally to the field of detection of movement of a light pattern, and more particularly pertains to a new and improved system which enables the rapid detection of movement of a light pattern or image.
Systems for detecting movements of light patterns have been widely used in many fields, and particularly have been used in photographic and electronic cameras for detecting movement of the image within the camera. For the case of a photographic system the image movement is detected and then either the film or the camera is moved to compensate for the image movement such that a clear and sharp photographic image is formed.
Several types of systems have been utilized in the prior art to determine image motion. Some of these prior art systems are types in which radiation from a moving scene is imaged on a black and white reticle such that the image moves across the reticle. Light transmitted through the reticle is focused on a detector. In those systems the electrical output signal of the detector has a major frequency component dependent upon the speed of movement of the image across the reticle. A problem with this type of system is that the frequency is modulated also by image detail entering or leaving the grid area, and accordingly the system suffers a loss of accuracy. A second type of prior art system involves placing two spaced photodetectors in the moving image and measuring the time difference between the signals of the photodetectors. A problem with this system is that image details must actually move over the two detectors before the time difference can be measured, and accordingly the response time is rather slow. Another known system in the prior art involves utilizing a rotating mechanical scanner which first scans the image and simultaneously magnetically records the output signal. The image is then mechanically scanned a second time, and the second signal is correlated with the stored signal to determine image movement. A problem with this type of system is that the use of a mechanical scanner and a single photo cell makes the system slow, cumbersome, and unattractive from a reliability standpoint.